Anorexia nervosa

Definition

• Anorexia nervosa is a restrictive eating disorder characterised by low body weight, intense fear of gaining weight, and a distorted body image
• Individuals restrict energy intake leading to significantly low body weight for age, sex, developmental trajectory, and physical health
• Subtypes include restricting type and binge-eating/purging type

DSM-5 Diagnostic Criteria

• Restriction of energy intake relative to requirements, leading to significantly low body weight
• Intense fear of gaining weight or becoming fat, or persistent behaviour that interferes with weight gain
• Disturbance in body image, undue influence of body weight on self-evaluation, or denial of seriousness of low weight
• Subtypes:
  • Restricting type: no bingeing or purging in last 3 months
  • Binge-eating/purging type: recurrent binge eating or purging in last 3 months

ICD-10 Classification (F50.0)

• Weight is maintained at least 15% below expected or BMI <17.5
• Self-induced weight loss through avoidance of food and/or purging, vomiting, excessive exercise
• Distorted body image
• Endocrine disturbance manifesting as amenorrhoea in females or loss of libido in males
• In prepubertal individuals, delayed or arrested puberty

Epidemiology (Australia)

• Lifetime prevalence: ~0.5–1%
• Onset typically in adolescence or early adulthood
• Significantly more common in females (up to 90%)
• Increasing recognition in males and gender-diverse populations
• One of the highest mortality rates among psychiatric conditions

Risk Factors

• Female sex and adolescent age
• Family history of eating disorders or mood disorders
• Perfectionism or obsessive-compulsive traits
• Childhood trauma or bullying
• Participation in weight-focused sports or activities
• Cultural and media pressures around body image
• Comorbid anxiety, depression, or OCD

Clinical Features

• Low body weight or weight loss despite reassurance from others
• Intense fear of weight gain despite being underweight
• Body image disturbance or denial of low weight
• Dietary restriction, food rituals, calorie counting
• Excessive exercise or purging behaviours
• Amenorrhoea or delayed menarche in females
• Cold intolerance, lanugo, dry skin, bradycardia, hypotension
• Social withdrawal and preoccupation with food or body shape
• Often accompanied by depressive and anxious symptoms

Screening Tools

• SCOFF questionnaire
• Eating Disorder Examination Questionnaire (EDE-Q)
• Consider BMI assessment and growth chart plotting in adolescents
• Ask about restrictive eating, purging, and body image concerns

Differential Diagnoses

• Bulimia nervosa (typically normal weight, recurrent bingeing and purging)
• Avoidant/Restrictive Food Intake Disorder (ARFID)
• Body dysmorphic disorder
• Depression with appetite suppression
• Gastrointestinal conditions (e.g., coeliac, IBD)
• Hyperthyroidism or other endocrine disorders
• Malabsorption syndromes

Investigations

• FBC (anaemia, leucopenia), electrolytes (especially potassium), renal function
• LFTs (may show elevation in starvation)
• TFTs (often low T3 syndrome)
• ECG (check for bradycardia, QT prolongation)
• BMD (DEXA scan) if amenorrhoea >6 months
• Hormones: LH, FSH, oestradiol in females; testosterone in males
• Urinalysis and blood glucose if at risk of hypoglycaemia

Complications

• Bradycardia, hypotension, hypothermia
• Electrolyte abnormalities (especially hypokalaemia)
• Amenorrhoea, infertility, osteoporosis
• Cardiac arrhythmias and sudden death
• Gastrointestinal symptoms (gastroparesis, constipation)
• Refeeding syndrome if rapidly refed
• Cognitive impairment, depression, suicide
• Chronic malnutrition and growth stunting (in adolescents)

Psychoeducation

• Provide clear, non-judgemental explanation of diagnosis
• Emphasise that anorexia is a treatable medical and psychological condition
• Involve family members, especially in adolescents
• Explain medical risks of malnutrition and importance of early treatment
• Discuss risk of refeeding syndrome and need for slow nutritional rehabilitation

Nutritional and Medical Management

• Re-nourishment is essential, preferably under dietitian guidance
• Monitor for refeeding syndrome (phosphate, magnesium, potassium)
• Correct dehydration and electrolyte imbalances
• Monitor vitals, weight, and intake regularly
• Hospitalisation indicated for severe medical instability or BMI <14 in adults
• In adolescents, family-based treatment should begin early

Psychological Therapy

• First-line treatment in all cases alongside medical care
• Family-Based Therapy (FBT) is first-line in adolescents
• Cognitive Behavioural Therapy – Enhanced (CBT-E) in adults
• Specialist eating disorder programs may offer group, individual, and day programs
• Address perfectionism, cognitive distortions, and body image disturbance

Pharmacological Treatment

• No medications are effective for core features of anorexia nervosa
• SSRIs may be considered for comorbid depression or OCD after weight restoration
• Olanzapine may reduce anxiety around eating and support weight gain (specialist use)
• Avoid appetite suppressants or medications with high metabolic risk
• Monitor for QT prolongation if prescribing psychotropics

Follow-Up and Monitoring

• Weekly or more frequent review during acute phase
• Monitor weight, vitals, electrolytes, and food intake
• Assess mental state, treatment adherence, and motivation
• Screen for ongoing purging or over-exercise
• Long-term monitoring due to high relapse risk

Referral and Escalation

• Refer to specialist eating disorder service early
• Hospitalisation if BMI <14, rapid weight loss, electrolyte abnormalities, or bradycardia
• Involuntary treatment under Mental Health Act may be required if patient lacks insight and is medically unwell
• Engage multidisciplinary team: GP, psychologist, dietitian, psychiatrist, paediatrician (for young people)

Support Resources

• Butterfly Foundation (1800 33 4673)
• Eating Disorders Victoria
• InsideOut Institute
• Headspace (for youth)
• Beyond Blue
• National Eating Disorders Collaboration (NEDC)